Heater Core Flush

[TN_OIL]

The system was also flushed about 5 years and about 25k

The system was also flushed about 5 years and about 25k ago

It's not a terribly challenging job, so I'd flush your system. Especially since you flushed your heater core and are still having issues.

 

[zulf200]

Ive used the poor mans version too, it has no pump, just a bucket with a pipe fitting on the bottom and put the bucket up high like on a ladder or shelf, have a pinch pliers to act as a valve.

Let it flow and collect it in another bucket,

The bucket also works a treat to fill long run cooling systems like the old toyota mr2.

 

[zulf200]

He may be just fine. I was having issues on my BMW with no heat on the passenger side and low heat on the drivers side. Shop flushed the heater core with just a garden hose and gunk came out and it was good for a year, but then problem returned.

The shop recommended I put Liqui Moly radiator flush in the car before driving to their shop (an hour away), then when I got there, they used this tool they had recently purchased:

Its been over two years, still heats fine. No leaks, no issue. Car is 24 years old and 371k miles.
The annoying thing is I only use factory BMW G48 coolant and get it changed every 3 to 4 years since new. Not sure why this black gunk was forming in the heater core.

View attachment 256622

The black gunk is usually some oil content which has reduced down and become a tarry grease, non foaming soap cleans it out. Liqui moly flush has good soaping action that emulsifies it.

Bmws are known for cooling systems issues and this is why I mandate a full system flush and clean if any thing leaks where oil and coolant are in close area like the oil filter housing or oil cooler.